1. Field of the Invention
This invention relates to a legged mobile robot control system, particularly to a system for controlling a legged mobile robot that is equipped with legs and arms attached to a body to be able to move by driving the legs, and to operate the arm to shake hands with a person.
2. Description of the Related Art
The prior art includes robots made capable of shaking hands with people so as to upgrade their ability to communicate with human beings, as taught by, for example, Japanese Laid-Open Patent Application No. 2004-283975, particularly paragraphs 0062 to 0066 and FIGS. 8 and 9. The robot taught by this reference has a pressure sensor embedded in its hand. During handshaking with a person, the person's gripping force is detected to make different utterances depending on the intensity of the detected gripping force. (It says “How do you do?” when the force is about right and “Ouch” when it is too strong.) It is also controlled to make an associated arm movement (pull its arm and hand inward when the gripping force is strong). These responses are intended to improve the robot's ability to communicate. (The robot of this reference is a wheeled mobile robot.)
When a robot is controlled to shake hands with a person, its arm receives a considerable external force. This does not cause a particular problem in the case of the robot set out in the reference because it is configured to move on wheels, so that it stay posturally stable despite the external force acting on its arm during handshaking. However, the external force applied by handshaking may well be strong enough to disturb the posture of a legged mobile robot, particularly a biped robot, that moves by driving legs. In other words, the posture of the legged mobile robot is liable to be destabilized by the action of shaking hands with a human.